Not all stations in a network may be in direct contact with each other.
If not, we will relay a message through an existing station. If the
planning of the event indicates that most of the stations probably won't be able
to speak to each other, we'll provide a separate relay station at a good radio
location.

A manual relay consists of the message being sent from A to B to C. If
relay B has talk-through facility, the message is sent on one frequency from A
to B. Relay B automatically retransmits the message on another
frequency. Station C listens on that other frequency.

An Amateur Radio repeater is at a designated fixed location and much
paperwork and planning is required before a licence is issued. The process
could take weeks or months. Any licensed Radio Amateur is allowed to use
an existing repeater.

RAYNET talk-through is a very similar thing, except it is done on an ad hoc
basis. Talk-through is used where it is needed at a particular
event. It is provided by and for the sole use of the RAYNET operators at
that event.

Talk-though Unit

A single talk-through facility is often enough to link the Control station
with all outstations.

Talk-through in tandem

To cover longer distances or larger areas, talk-through units can be made to
work one after another.

In the above diagram, Control could be in Stockton-on-Tees, the first TTU
could be on a hill overlooking Stockton and the second TTU could be on a hill
overlooking Durham City.

Alternatively, Control could be in an underground room in Middlesbrough, the
first TTU could be in a nearby car park and the second TTU could be on a hill
overlooking Middlesbrough.